In many modern cable television systems the system operator has the capability of communicating with the plurality of subscriber terminals that are connected via the cable to the system headend via a cable distribution system. In a typical cable system, each subscriber terminal is provided with a converter which is assigned a unique address that permits the headend to communicate with the subscriber to, for example, establish in the converter a program authorization code that determines which pay program or programs that subscriber will be able to receive. In many cable systems, the subscriber is also able to communicate with the headend in a two-way communication link, so as to permit each subscriber terminal to be interrogated or addressed from the headend to, for example, bill the subscriber for viewing special events or poll the subscriber as part of a survey or opinion poll. Such two-way communication also requires that each subscriber terminal be assigned a unique address to permit the headend to be able to identify that terminal with which it is either sending information to or receiving information from.
Moreover, particularly when a relatively large number of subscriber terminals are connected to a headend in a cable transmission system, it is highly advantageous, in terms of saving time, for the headend to be able to address the subscriber terminals in a numerical sequence. This would enable, for example, successively numbered subscriber terminals to be addressed in sequence simply by modifying one or two of the least significant bits of the address code for each subscriber terminal, rather than as many as 21 bits, which may be required when addressing is performed in a nonsequential manner.
The subscriber terminal address is conventionally stored in a programmable read-only-memory (PROM) at or prior to the time the converter is installed at the subscriber's home. This is done in the field by the installer by the use of a PROM programmer. The installer programs the PROM with the preassigned logical address for that subscriber and installs the PROM into a socket provided for the PROM in the subscriber's converter. The subscriber terminal address may also be programmed to store the subscriber's address by cutting selected jumper wires or by operating a series of switches to establish the desired address code in the PROM.
This procedure is, however, time-consuming and costly and inefficient, and must be repeated in the field each time a new converter is installed at a subscriber's home. In addition, it is difficult for the system operator to keep accurate records of the addresses that have been allocated or assigned to the subscribers on the system.
It is accordingly an object of the present invention to provide an addressable cable TV converter in which an unique address can be loaded or stored from a remote headend controller.
It is a further object of the present invention to provide an addressable converter, which, when a plurality are employed in a single cable transmission system, allows the converter to be given sequential address codes.
It is another object of the present invention to provide an addressable converter of the type described which need not be mechanically handled or mechanically modified after its manufacture.
To these ends, the addressable CATV converter of the invention includes a programmable read-only memory in which a unique identification code for the converter is stored, and a random-access memory (RAM) which can be programmed with the unique assigned converter address after the converter is installed at the subscriber location. The converter includes a data receiver which, when the converter is connected to the cable receives from the headend a unique preassigned address code corresponding to the unique identification code stored in the PROM. When the identification code stored in the converter PROM is matched at the converter with the received identification code, the unique preassigned address code is stored into the converter RAM, thereby to enable the headend to thereafter efficiently communicate with the converter.